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Pseudo-hexagonal packing

These phases very often share, aside from a relatively high disorder, another important feature with the bundle-like pre-crystalline entities that we discussed up to this point. This feature is hexagonal or pseudo-hexagonal packing of the polymer chains [61]. In this respect molecular order at a local level is similar, although in the thermotropic mesophases we are now discussing disorder is even more dynamic than in previous cases. Indeed they are essentially characterized by a high entropy. [Pg.102]

Figure 1.6. Schematic diagram of four unit cells of /rons-polyacetylene showing pseudo-hexagonal packing and in phase and 180° out of phase relationships of the double and single bonds between nearest neighbours. (Reproduced from ref. 59 with kind permission. Copyright (1987) Elsevier Science Ltd, Kidlington 0X5 IGB, UK.)... Figure 1.6. Schematic diagram of four unit cells of /rons-polyacetylene showing pseudo-hexagonal packing and in phase and 180° out of phase relationships of the double and single bonds between nearest neighbours. (Reproduced from ref. 59 with kind permission. Copyright (1987) Elsevier Science Ltd, Kidlington 0X5 IGB, UK.)...
Main-chain LCPs that exhibit nematic order tend towards pseudo-hexagonal packing in the liquid-crystalline state. Wide-angle X-ray-diffraction... [Pg.383]

The X-ray fiber diffraction patterns of form II show two equatorial reflections and a diffuse meridional 002 reflection [66,165]. The equatorial reflections indicate a pseudo-hexagonal packing of chain axes with a = 4.88 A and c = 4.65 A [66]. During the transition from form I into form II, the c axis shrinks by 4% while the distance between the chain axes increases by 7.5% and the volume per chain in the crystalline state increases by 9% [8]. [Pg.23]

The structure of rutile, Ti02-x, is tetragonal, with a pseudo-hexagonal packing of oxygen ions in the (001) plane (space group P42/mnm). Rutile is commonly oxygen deficient. It is an ore for titanium and occurs in quartz veins in metamorphic rocks and as placer deposits. [Pg.198]

Fig. 9 Two arrangements of helical chains, represented as continuous screws, packing in a hexagonal or a pseudo-hexagonal mode. In a the three screws are isomorphous in b the screw B is enantiomorphous with respect to both A and C and the overall packing is less satisfactory. Reproduced with permission from [13]. Copyright 1998 Am Chem Soc... Fig. 9 Two arrangements of helical chains, represented as continuous screws, packing in a hexagonal or a pseudo-hexagonal mode. In a the three screws are isomorphous in b the screw B is enantiomorphous with respect to both A and C and the overall packing is less satisfactory. Reproduced with permission from [13]. Copyright 1998 Am Chem Soc...
Up to 2% authigenic kaolinite and dickite occur in host rocks as loosely packed booklets of pseudo-hexagonal crystals (5-15 pm). They occur on authigenic quartz overgrowths and on partly dissolved feldspar grains. [Pg.201]


See other pages where Pseudo-hexagonal packing is mentioned: [Pg.90]    [Pg.98]    [Pg.112]    [Pg.114]    [Pg.298]    [Pg.92]    [Pg.100]    [Pg.114]    [Pg.116]    [Pg.108]    [Pg.384]    [Pg.22]    [Pg.472]    [Pg.359]    [Pg.7]    [Pg.332]    [Pg.356]    [Pg.90]    [Pg.98]    [Pg.112]    [Pg.114]    [Pg.298]    [Pg.92]    [Pg.100]    [Pg.114]    [Pg.116]    [Pg.108]    [Pg.384]    [Pg.22]    [Pg.472]    [Pg.359]    [Pg.7]    [Pg.332]    [Pg.356]    [Pg.97]    [Pg.112]    [Pg.116]    [Pg.117]    [Pg.118]    [Pg.121]    [Pg.153]    [Pg.121]    [Pg.9]    [Pg.21]    [Pg.422]    [Pg.181]    [Pg.99]    [Pg.114]    [Pg.118]    [Pg.119]    [Pg.120]    [Pg.123]    [Pg.1326]    [Pg.293]    [Pg.110]    [Pg.367]    [Pg.410]    [Pg.28]   
See also in sourсe #XX -- [ Pg.4 , Pg.108 , Pg.383 ]




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Hexagonal

Hexagons

Pseudo-hexagonal

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